1. Field of the Invention
This invention relates to an oscillation controller for an oscillating body and, specifically, to an oscillation controller capable of adjusting acceleration of the oscillating body.
2. Description of the Related Art
A machine tool such as a machining center includes an oscillating table for holding a work. The work is tilted due to oscillation of the oscillating table about an axis of rotation that extends, for example, in a horizontal direction. The work is then machined into a desired shape by a tool that moves relative to the work. The oscillating table is oscillated about the axis of rotation by an output torque of a servo motor. Since the center of gravity of the oscillating table is at a predetermined distance from the axis of rotation in a radial direction, a load torque is exerted by action of gravity. The load torque varies, depending upon an angular position of the oscillating table about the axis of rotation. If the load torque acts in a direction in which it hinders the oscillation of the oscillating table, the torque that accelerates or decelerates the oscillating table corresponds to a torque that is a resultant value of the subtraction of the load torque from the output torque of the servo motor. Reference should be made to JP-A-2011-44081 and JP-A-2010-262467.
Currently, the acceleration of the oscillating body when oscillating has been fixed. Specifically, an acceleration of the oscillating body is calculated by subtracting a maximum load torque that hinders the oscillation of the oscillating body from a maximum output torque of a servo motor and further dividing a resultant value of the subtraction by inertia about the axis of rotation. Therefore, at an angular position where the effect of gravity is relatively small, i.e., where the load torque is relatively small, only a lower torque is applied, even though a greater torque can be potentially applied. As a result, a relatively small acceleration is set, and thus, the torque of the servo motor cannot be effectively utilized.
The present invention was conceived in view of the above-mentioned circumstances. Thus, the object of the present invention is to provide an oscillation controller for an oscillating body capable of adjusting the acceleration of the oscillating body when the oscillating body oscillates.